International environmental experts warned this week that hydropower dams to be built on the Mekong River will have serious and long-term impacts on the environment and livelihoods of millions of people living along the river, especially those at its lower reaches in Laos and Cambodia.

They urged these countries to carefully consider impacts that have already been experienced in some of the developed world.

“The problem is not really about development and rights to development but it is about what kind of development, a short-term goal versus long-term cost,” Richard Cronin, director of the Southeast Asia Program of Henry L. Stimson Centre, told an auditorium organized by East-West Centre in Washington.

The use of hydropower and large dams as a source of energy “is extremely controversial, and particularly one of the most controversial things about it is old thinking,” he said. “We are now in this country trying to undo a lot of the damage that we did to rivers, especially in fisheries, from these big dams that we put up in 1930s.”

There are currently 11 hydropower dams planned for Laos and Cambodia. Two are in Cambodia. China, Thailand, Vietnam and Malaysia are main developers, with China playing a major role by taking four projects.

According to environmental experts, dam construction could affect water levels and cause erosion. This will subsequently have serious impacts on fish populations and people who rely on fisheries. It will also block the flow of fertile soil, which is important for agriculture.

“It actually creates a physical block to fish migration, and there are many species of fish that migrate from the Tonle Sap and some other parts of the flooded zone up into the Mekong mainstream,” said Blake Ratner, the regional director of the World Fish Center, an international organization based in Phnom Penh.

“They migrate up into tributaries in the upland within Cambodia, but also through the mainstream to Laos and even to northern Laos,” he told VOA Khmer by phone. “So to put a dam that blocks this fish migration means that it puts at risk a great majority of the piece that is important to the commercial catch.”

Out of many hydropower dams planned, Laos’s Don Sahong dam, located near the Cambodian border, has caused a lot of controversy and debate. It is feared that the impacts it has are vast, compared to the 300-some megawatts of power it is expected to generate.

“The Don Sahong dam will seriously affect fish populations, and we are discussing this with Laos since we are in the Mekong River family,” Sin Niny, vice chairman of Cambodia National Mekong Committee, told VOA in a phone interview. “Laos said that once they have finished their study, they will share the findings with us in a stakeholder forum for inputs.”

Even as it worries about developments upriver, Cambodia is looking at the possibility of developing a hydropower dam called Sambo in the northern province of Kratie, under an investment from China. The study for that dam is due to finish in 2010.

“The oil crises that happened in the past make us realize that we cannot leave aside resources that we can use to produce a cheap electrical supply,” Sin Niny said. “It is sustainable. We don’t need to buy others’ oil.”

The Sambo dam could provide 2,600 megawatts of electricity, and through other hydro-development schemes, the country is expected to be energy self-sufficient by 2012 and able to export power four years after that.

However, Cronin suggested that a regional power supply was a better choice. A hydropower dam should be built in the upper Mekong, where it would do no harm to fish migration, the Don Sahong and Sambo dams abandoned, he said.

“You could consider building a dam where the cost benefit is the best and then sharing that power in the region,” he said. “Of course you can build the dam in northern Laos, where it would not have anywhere near the impacts on fishery that these two other Mekong dams would have.”

The Mekong River flows for 4,880 kilometres from its headwaters in Tibet, then through Burma, Laos, Thailand, Cambodia and Vietnam, one of the largest sources of freshwater fish in the world.